The invention relates to an electrical rotary speed generator for producing an electrical signal, which provides a signal representative of the angular speed between two components rotating relative to each other. Such a generator has been described in our U.S. Pat. No. 3,793,545 in which a rotor is arranged on a rotating component and provided with equispaced recesses or teeth and a stator displaceably held on the stationary component by means of elastic clamping bodies, which stator extends only over a small angular region of the rotor and has its pole facing opposite the rotor recesses. The rotor and stator are provided with sliding surfaces, which permit a harmless contact between rotor and stator, so that, after setting the stator to a minimum air gap on assembly, radial relative movements of the components with respect to each other cause a displacement of the stator in a direction to enlarge the air gap after frictional adhesion of the stator to its mounting is overcome.
The invention in this Prior Patent is based on the knowledge that if the air gap of such a signal generator is merely determined by the relative movements of the components with respect to each other, it is still adequately small, but, however, a further enlargement of the air gap caused by tolerances is not admissible.
For this purpose the stator is so constructed that, on the assembly the air gap with regard to the sliding surfaces is automatically zero, and thus stator and rotor abut each other. However, on the other hand, the stator is so flexibly arranged that clamping is avoided. However, this flexibility is not an elastic flexibility but a flexibility in the sense of a frictional adhesion so that the rotor creates only as much space as it requires for its rotation and the stator remains in the position into which it was displaced.
Thus it is characteristic of the rotary speed signal generator of the Prior Patent that the variations of the magnetic air gap are caused by wheel bearing play movements. In operation after the respective positions of rotor and stator have been determined by the rotor, the stator is located stationarily on the non-rotatable component adjacent to the rotor, which is firmly connected to the rotatable component, so that sprung or loose coupling elements for the stator are not necessary.
If the housing of the stator of such a signal generator is proposed to be made of plastics material and is inserted in a bore of the stationary component, than it is possible -- because of the different function of temperature of the plastics material and the material of the stationary component -- that the stator will be firmly seated in its bore and can no longer be displaced. Therefore with relative movements of the components towards each other, destruction of the signal generator follows, since the stator can no longer be displaced. On the other hand, a large amount of play cannot be permitted between the stator and the wall of the bore, since the stator must be exactly guided through the bore in order to avoid erroneous signals.